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Clipper circuit with using ADA4851

kabekami
on Jul 1, 2019

Hi , 

I am checking a Clipper circuit  with ADA4851. 

And when simulate with various voltage , I find a relation between the Voltage at non inverting and supply voltage .

When using in 0-5V supply , +3V at non inverting terminal i see that the out is clamped but is looks different , is this expected .

I do understand the circuit in open loop when the diode is off . 

Thanking you 

With best regards and wishes 

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  • +1
    •  Analog Employees 
    on Jul 2, 2019 7:27 AM over 1 year ago

    Hi,

    What you're seeing is normal. When the input voltage(V6) is below reference, the op amp's output is driven to the positive rail and the diode will then be in reversed-biased condition. The op amp is in open-loop configuration during this period.

    Remember that the op-amp's output headroom is dependent on the load current it sinks or sources(output voltage saturation vs load current graph). The diode even though in reverse bias has leakage current that flows through it, this is very minimal but remember that the output voltage is operating at the supply-rail range and is very sensitive to change with respect to load current(sine-wave input, R2). That's what you are seeing at the output. Headroom changing due to load current.

    Hope this clears things up.

    Regards,
    Goz



Reply
  • +1
    •  Analog Employees 
    on Jul 2, 2019 7:27 AM over 1 year ago

    Hi,

    What you're seeing is normal. When the input voltage(V6) is below reference, the op amp's output is driven to the positive rail and the diode will then be in reversed-biased condition. The op amp is in open-loop configuration during this period.

    Remember that the op-amp's output headroom is dependent on the load current it sinks or sources(output voltage saturation vs load current graph). The diode even though in reverse bias has leakage current that flows through it, this is very minimal but remember that the output voltage is operating at the supply-rail range and is very sensitive to change with respect to load current(sine-wave input, R2). That's what you are seeing at the output. Headroom changing due to load current.

    Hope this clears things up.

    Regards,
    Goz



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